Transient signals in an electrical circuit can cause a number of problems in certain applications. Transient signals that have sufficiently high voltage or current can damage electrical circuitry or otherwise adversely affect performance of one or more components. A transient voltage is usually the result of a sudden, sharp change in voltage across a circuit component that is often is associated with initiating power to a load. In some applications, transient signals may not damage components, but nonetheless provide undesirable effects and/or reduce performance.
In a number of applications, particularly relating to audio systems, it is desirable to eliminate or substantially reduce transient voltages across certain loads to reduce adverse impacts of such transient voltage on performance. Click/pop is one such undesirable result of transient voltages. Click/pop is an unpleasant audible artifact provided by a loudspeaker (or speaker), which is often heard when an audio system powers up or powers down. Click/pop is generally caused by a transient voltage drop (e.g., a DC offset mismatch) across a speaker that may occur when a power amplifier transitions between a non-switching mode and a switching mode.
The audibility of click/pop does not depend only on the energy involved, but also on how the energy spectrum is shaped. While click/pop is most often heard when the audio amplifier system is powered on, click/pop can also occur when the audio system is powered down, or when the audio system changes mode. The mode changes can include changing from surround mode to stereo mode, from stereo to mono mode or between different surround sound modes.